A handover refers to a technique that allows a moving terminal (mobile terminal) to continue its current data communication when it moves out of the cell area of one base station and enters the cell area of another base station.
In other words, as illustrated in FIG. 1, when a mobile terminal 130 moves out of the cell area of a first base station 110, with which a data communication is currently taking place, and enters the cell area of an adjacent second base station 120, the mobile terminal 130 may perform a handover from the first base station 110 to the second base station 120 for seamless data communication.
Handovers can be divided mainly into horizontal handovers (or homogeneous handovers), performed when a mobile terminal moves across networks of the same type, to which the same technology is applied, and vertical handovers (or heterogeneous handovers), performed when a mobile terminal capable of multiple accesses (multiple interfaces) moves across access networks of different types, to which different technology is applied. For example, a vertical handover may be performed when a mobile terminal moves between a WiBro network and a WLAN network, a WLAN network and a CDMA network, or between a 3G network and a WLAN network.
In the case of a vertical handover between access networks of different types, in particular, service disruption may occur during the process of starting communication with a base station according to mutually different access technologies, creating a risk of data loss. However, conventional methods of performing vertical handovers focus mainly on improving the accuracy of handover decisions, such as by mitigating the ping-pong effect, and thus may face difficulties in guaranteeing the QoS (quality of service).